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NEW COSMOS Electrical CO. | Date: 2014-06-18

A controlled potential electrolysis gas sensor including, as gas electrodes

Kuse T.,New Cosmos Electrical Co. | Kanda K.,New Cosmos Electrical Co.
International Gas Research Conference Proceedings | Year: 2014

A new type of GC called the XG-1 00 that uses a semiconductor gas sensor to measure odorants, e.g., THT (tetrahydrothiophene), DMS (dimethyl sulfide), TBM (tertiary-butyl mercaptan) and cyclohexene, is developed. The GC is designed to use in identifying whether the gas detected by a detector is the result of leakage from underground pipelines that supply town gas or is naturally occurring gas. This GC can be used to detect between 10 ppb and several tens of ppb of THT, DMS, TBM, and cyclohexene, without sample enrichment. The device uses ambient air as the carrier gas so there is no need for highly pressured cylinder gas of N2, He, or H2, which are indispensable for normal GC systems. This is an abstract of a paper presented at the International Gas Union Research Conference (IGRC 2014) (Copenhagen, Denmark 9/17-19/2014).

Wongwiriyapan W.,King Mongkuts University of Technology Thonburi | Okabayashi Y.,Osaka University | Minami S.,Osaka University | Itabashi K.,Osaka University | And 7 more authors.
Nanotechnology | Year: 2011

Protective-layer-coated single-walled carbon nanotubes (SWNTs) with palladium nanoparticle decoration (Pd-SiO2-SWNTs) were fabricated and their sensing properties for hydrogen (H2) were investigated. SWNTs were coated with a 3-4 nm thick SiO2 layer by pulsed laser deposition and subsequently decorated with Pd nanoparticles by electron beam evaporation. Even though the SWNTs were completely surrounded by a protective layer, Pd-SiO2-SWNTs responded to H2 down to a concentration of 1 part per million. Compared with the Pd nanoparticle-decorated SWNTs without a protective layer (Pd-SWNTs), Pd-SiO2-SWNTs exhibited highly stable sensor responses with variations of less than 20%; Pd-SWNTs showed a variation of 80%. The density of the Pd-SWNTs significantly decreased after the sensing test, while that of the Pd-SiO2-SWNTs with the netlike structure remained unchanged. The hydrogen sensing mechanism of the Pd-SiO 2-SWNTs was attributed to the chemical gating effect on the SWNTs due to dipole layer formation by hydrogen atoms trapped at the Pd-SiO2 interface. Moreover, the relationship between H2 concentration and sensor response can be described by the Langmuir isotherm for dissociative adsorption. © 2011 IOP Publishing Ltd.

Itabashi K.,Osaka University | Tabata H.,Osaka University | Wongwiriyapan W.,King Mongkuts University of Technology Thonburi | Minami S.,Osaka University | And 5 more authors.
Japanese Journal of Applied Physics | Year: 2012

We fabricated single-walled carbon nanotubes (SWNTs) covered with a thickness-controlled ZnO layer (ZnO-SWNTs) by pulsed laser deposition (PLD) and investigated their UV photoresponse, induced by the photodesorption of oxygen molecules from the ZnO surface. The magnitude of the negative photocurrent and the recovery time were strongly dependent on the thickness and morphology of the ZnO layer, and were highest when the ZnO layer was 3-4nm thick. The observed recovery curves of the negative photocurrent were fitted with double-exponential-function curves, which indicate the coexistence of two types of adsorption sites for oxygen molecules on the ZnO surface. The light intensity dependence of the negative photocurrent was also measured. © 2012 The Japan Society of Applied Physics.

Itoh T.,Japan National Institute of Advanced Industrial Science and Technology | Taguchi Y.,Japan National Institute of Advanced Industrial Science and Technology | Izu N.,Japan National Institute of Advanced Industrial Science and Technology | Matsubara I.,Japan National Institute of Advanced Industrial Science and Technology | And 5 more authors.
Sensor Letters | Year: 2011

The response of CeO2 to H2S has been investigated by an alternating current (AC) impedance analysis. The AC impedance analysis can divide whole impedance, i.e., identical with direct current resistance, to three type contributions, bulk, grain boundary, and electrode interface. In a case of CeO2, the bulk contribution is the main component of the whole impedance because of clear grain boundary, which is observed by a transmission electron microscope observation. Sensor responses are defined as the quotient of sensor resistance in no odor air and sensor resistance in odor. The sensor responses of bulk contribution are almost identical with those of whole impedance. Copyright © 2011 American Scientific Publishers. All rights reserved.

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